Can anyone tell me where the location is for the coolant temp sensor on a 1999 f150 4.6 L

 

Easiest way to get to it is to take the Air intake plastics off, then take the Alternator off. Look down to the right under the Intake manifold and you'll see it. It has a few wires clipped to it at the top. You need a long open end wrench to get it out. You can't get a socket or a crescent wrench in there. I believe it's 13/16 but I could be wrong.

If your sensor failed you're probably going to have to replace all 8 of your sparkplugs like I just had to do. I had this problem about a month ago. Sensor went out and it ran so rich that it fouled all 8 of my plugs.

(oh yea also, its a Cylinder Head Temperature Sensor on the 99's.)